Added single integration test

Author: nametake

go.mod

@@ -3,3 +3,5 @@ module github.com/nametake/golangci-lint-langserver
 go 1.23.4
 
 require github.com/sourcegraph/jsonrpc2 v0.0.0-20191222043438-96c4efab7ee2
+
+require github.com/google/go-cmp v0.6.0

go.sum

@@ -1,3 +1,5 @@
+github.com/google/go-cmp v0.6.0 h1:ofyhxvXcZhMsU5ulbFiLKl/XBFqE1GSq7atu8tAmTRI=
+github.com/google/go-cmp v0.6.0/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
 github.com/gorilla/websocket v1.4.1 h1:q7AeDBpnBk8AogcD4DSag/Ukw/KV+YhzLj2bP5HvKCM=
 github.com/gorilla/websocket v1.4.1/go.mod h1:YR8l580nyteQvAITg2hZ9XVh4b55+EU/adAjf1fMHhE=
 github.com/sourcegraph/jsonrpc2 v0.0.0-20191222043438-96c4efab7ee2 h1:5VGNYxMxzZ8Jb2bARgVl1DNg8vpcd9S8b4MbbjWQ8/w=

handler_test.go

@@ -0,0 +1,59 @@
+package main
+
+import (
+	"os/exec"
+	"path/filepath"
+	"testing"
+
+	"github.com/google/go-cmp/cmp"
+)
+
+func pt(s string) *string {
+	return &s
+}
+
+func TestLangHandler_lint_Integration(t *testing.T) {
+	_, err := exec.LookPath("golangci-lint")
+	if err != nil {
+		t.Fatal("golangci-lint is not installed in this environment")
+	}
+
+	testFilePath, _ := filepath.Abs("./testdata/simple/main.go")
+
+	h := &langHandler{
+		logger:  newStdLogger(false),
+		command: []string{"golangci-lint", "run", "--out-format", "json", "--issues-exit-code=1"},
+		rootDir: filepath.Dir(testFilePath),
+	}
+
+	testURI := DocumentURI("file://" + testFilePath)
+
+	diagnostics, err := h.lint(testURI)
+	if err != nil {
+		t.Fatalf("lint() returned unexpected error: %v", err)
+	}
+
+	want := []Diagnostic{
+		{
+			Range: Range{
+				Start: Position{
+					Line:      2,
+					Character: 4,
+				},
+				End: Position{
+					Line:      2,
+					Character: 4,
+				},
+			},
+			Severity:           DSWarning,
+			Code:               nil,
+			Source:             pt("unused"),
+			Message:            "unused: var `foo` is unused",
+			RelatedInformation: nil,
+		},
+	}
+
+	if diff := cmp.Diff(want, diagnostics); diff != "" {
+		t.Errorf("lint() mismatch (-want +got):\n%s", diff)
+	}
+}